1. Field of the Invention
The present invention relates generally to a system for mounting and installing photovoltaic solar panels.
2. Description of the Related Art
With the continual rise in conventional energy costs, photovoltaic solar panels (“PV panels”) are increasingly becoming cost competitive with other types of energy generation. These PV panel systems are being installed in sites of high energy usage, such as on commercial building rooftops, in industrial open areas, and in proximity to substations tied to the electric grid. These commercial energy systems, or power plants, vary in size but can cover many thousands of square feet on a building rooftop and many acres of land when installed on the ground. Roof mounted systems are particularly attractive in that business owners can elect to offset the energy consumption of their facilities through the use of existing space on the tops of their buildings.
However, such large solar arrays require a sufficiently strong support structure to support not only the weight of the array, but to also provide sufficient resistance to wind forces. Tightly spaced panels effectively form a large surface area, which could result in damage to the panels, the support structure, or both, under strong wind conditions. In addition these systems must accommodate a variety of roof types including built-up roof membranes, monolithic, synthetic membranes, and shingled, mineral surfaces. In order to respond to a variety of roof deck surfaces the mounting structures must provide flexibility in contact elements and attachment systems. These systems must balance the benefits of greater weight, or ballast, to resist wind forces and the load limits of the buildings upon which they are being placed which in many cases were designed to take people walking on them but not the additional load of a large mechanical array.
In many installations, the solar panels are mounted in a “tilted” or inclined configuration in order to maximize the effective capture of solar radiation, i.e. the solar panels are aligned with the solar angle of incidence. In mounting tilted solar panels, however, the effects of various loads on the mounting surface, such as a roof, must be understood. The loads include standing loads and variable loads, also commonly called dead loads and live loads, respectively.
Standing loads are the result of the combined weight of the solar panels and the mounting system. These standing loads are predictable and are therefore easier to accommodate for during the installation of the solar panels and the mounting system.
Variable loads on the tilted solar panels are mainly caused by environmental conditions, such as wind, rain, snow, hail, etc. Other potential environmental hazards include seismic events, temperature extremes, debris and mold. In order to be able to reliably predict and accommodate variable loads, these environmental problems have to be understood and resolved. The most common and problematic forces are wind-related forces (including hurricanes and tornados), namely lift and drag forces generated by the wind conditions. A variety of mounting systems have been commercially available for mounting solar panels, which have attempted to address and mitigate the wind-induced forces. Most prior mounting systems can be divided into three general categories: non-tilted solar arrays; enclosed tilted solar arrays; and tilted solar panels with wind deflectors attached to every row.
U.S. Pat. Nos. 5,746,839 (Dinwoodie) and U.S. Pat. No. 6,570,084 (Dinwoodie) are examples of implementations involving non-tilted solar panels. While non-tilted solar panels do present a lower profile with respect to wind forces, they are less efficient at converting solar energy to electrical energy when installed at locations with higher latitudes. Another disadvantage of a non-tilted system is the accumulation of dirt, dust, debris and snow on top of the solar panels, which can further reduce the conversion efficiency of the panels.
U.S. Pat. No. 6,968,654 (Moulder) discloses an example of an enclosed tilted solar panel system. While such a design offers advantages such as improved rigidity, less debris accumulation, and better protection of electrical components, an enclosed solar panel system increase the cost and weight of the system, is likely to increase wind-induced drag forces and also significantly reduces beneficial cooling from natural airflow. The additional heat introduced into the panels by the mounting system results in lower energy output from the photovoltaic panels.
As shown in U.S. Pat. Nos. 6,063,996 (Takada), U.S. Pat. No. 6,809,251 (Dinwoodie) and U.S. Publication No. 2004/0250491 (Diaz), deflectors may be installed on the north-facing back of every panel in order to reduce the wind-induced uplift forces, when installed in the northern hemisphere. Disadvantages of such systems include significantly increased cost and weight of the installed system. These systems also increase the required labor time for installation in that more parts must be assembled in order to complete the array. In addition, reduced cooling of the solar panels can also significantly reduce the solar conversion efficiency of the system.
It will also be apparent to one skilled in the art that solar panels or modules having extruded metal frames will present different challenges in mounting than those that are produced without additional framing elements. The latter type of solar panels are often referred to as laminates as they are an assembly of one or two sheets of glass along with the photovoltaic material and backing sheet materials to form a laminated assembly. The attachment of these frameless modules, or laminates, is a mechanical challenge often met with the use of clips or hooks that pull one edge of the module into close contact with a supporting structure. Another method of making this connection is to clamp the edge of the module directly and then provide a mounting structure within the sub-structure of the array to hold the module mounting clamp.